Orthopedic leg alignment system and method

ABSTRACT

An orthopedic measurement system is disclosed to measure leg alignment. The measurement system includes a tri-axial gyroscope configured to measure movement of a leg. The gyroscope is coupled to a tibia of the leg. For example, the gyroscope can be placed in an insert or tibial prosthetic component that couples to the tibia. The gyroscope is used to measure alignment relative to the mechanical axis of the leg. The leg alignment measurement is performed by putting the leg through a first leg movement and a second leg movement. The gyroscope outputs angular velocities on the axes the sensor is rotated about. The gyroscope is coupled to a computer that calculates the alignment of the leg relative to the mechanical axis from the gyroscope measurement data.

FIELD

The present invention pertains generally to measurement of physicalparameters, and particularly to, but not exclusively to, measuringorthopedic alignment.

BACKGROUND

The musculoskeletal system of a mammal is subject to variations amongspecies. Further changes can occur due to environmental factors,degradation through use, and aging. A joint of the musculoskeletalsystem typically comprises two or more bones that move in relation toone another. Movement is enabled by muscle tissue and tendons that is apart of the musculoskeletal system. Ligaments can position, hold, andstabilize one or more bones of a joint. Cartilage is a wear surface thatprevents bone-to-bone contact, distributes load, and lowers friction.

There has been substantial growth in the repair of the humanmusculoskeletal system. In general, prosthetic joints have evolved usinginformation from simulations, mechanical prototypes, and patient datathat is collected and used to initiate improved designs. Similarly, thetools being used for orthopedic surgery have been refined over the yearsbut have not changed substantially. Thus, the basic procedure forcorrection of the musculoskeletal system has been standardized to meetthe general needs of a wide distribution of the population. Although thetools, procedure, and artificial replacement systems meet a generalneed, each replacement procedure is subject to significant variationfrom patient to patient. The correction of these individual variationsrelies on the skill of the surgeon to adapt and fit the replacementjoint using the available tools to the specific circumstance. It wouldbe of great benefit if a system could be developed that improvessurgical outcomes and reduces the cost and time of a surgery.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features of the system are set forth with particularity in theappended claims. The embodiments herein, can be understood by referenceto the following description, taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an illustration of a leg in accordance with an exampleembodiment;

FIG. 2 is an exploded view of a prosthetic knee joint in accordance withan example embodiment configured to measure alignment of a leg;

FIG. 3 is an illustration of a prosthetic component incorporating atri-axial gyroscope in accordance with an example embodiment;

FIG. 4 is an illustration of a gyroscope in accordance with an exampleembodiment;

FIG. 5 is a block diagram of the gyroscope and electronic circuitry inaccordance with an example embodiment;

FIG. 6 is an illustration of angles measured by a gyroscope coupled to aproximal end of a tibia in accordance with an example embodiment;

FIG. 7 is an illustration of a first movement of a leg in accordancewith an example embodiment;

FIG. 8 is an illustration of a second movement of the leg in accordancewith an example embodiment;

FIG. 9 is an illustration of the required lower extremity measurementsfrom a patient in a sitting position in accordance with an exampleembodiment;

FIG. 10 is an illustration of a clinical flow to measure alignment of aleg in accordance with an example embodiment;

FIG. 11 is an illustration of a software flow to measure alignment of aleg in accordance with an example embodiment;

FIG. 12 is a block diagram of a measurement system or computer inaccordance with an example embodiment;

FIG. 13 is an illustration of a communication network for measurementand reporting in accordance with an exemplary embodiment; and

FIG. 14 is an illustration of a prosthetic knee joint including thetri-axial gyroscope in accordance with an example embodiment.

DETAILED DESCRIPTION

Embodiments of the invention are broadly directed to measurement ofphysical parameters, and more particularly, to a system that supportsaccurate measurement, improves surgical outcomes, reduces cost, reducestime in surgery.

The following description of exemplary embodiment(s) is merelyillustrative in nature and is in no way intended to limit the invention,its application, or uses.

Processes, techniques, apparatus, and materials as known by one ofordinary skill in the art may not be discussed in detail but areintended to be part of the enabling description where appropriate. Forexample specific computer code may not be listed for achieving each ofthe steps discussed, however one of ordinary skill would be able,without undo experimentation, to write such code given the enablingdisclosure herein. Such code is intended to fall within the scope of atleast one exemplary embodiment.

In all of the examples illustrated and discussed herein, any specificmaterials, such as temperatures, times, energies, and materialproperties for process steps or specific structure implementationsshould be interpreted to be illustrative only and non-limiting.Processes, techniques, apparatus, and materials as known by one ofordinary skill in the art may not be discussed in detail but areintended to be part of an enabling description where appropriate. Itshould also be noted that the word “coupled” used herein implies thatelements may be directly coupled together or may be coupled through oneor more intervening elements.

Additionally, the sizes of structures used in exemplary embodiments arenot limited by any discussion herein (e.g., the sizes of structures canbe macro (centimeter, meter, and larger sizes), micro (micrometer), andnanometer size and smaller).

Notice that similar reference numerals and letters refer to similaritems in the following figures, and thus once an item is defined in onefigure, it may not be discussed or further defined in the followingfigures.

In general, prosthesis is an artificial body part. An orthopedic implantis a device used to repair the musculoskeletal system. Common examplesof an orthopedic implant are pins, rods, screws, cages, plates and otherdevices that typically couple to bone of the musculoskeletal system. Aprosthetic joint can be part of a system that supports movement of themusculoskeletal system. A prosthetic joint typically comprises severalprosthetic components that combine to mimic a natural joint. Forexample, a prosthetic hip joint comprises an acetabular shell, anacetabular bearing, and a femoral prosthetic component. The acetabularshell couples to the pelvis and is a pivot point of the joint. Theacetabular bearing fits in the acetabular shell and provides a bearingsurface that supports hip movement. The femoral prosthetic componentcomprises a femoral head and a femoral hip stem. The head couples to thehip stem and fits into the acetabular bearing to distribute loading tothe bearing surface. The femoral hip stem couples to the proximal end ofthe femur. Thus, a prosthetic hip joint is a ball and socket joint thatcouples the femur to the pelvis to support movement of the leg.Similarly, prosthetic components are available to repair the knee,ankle, shoulder, hand, fingers, wrist, toes, spine and other areas ofthe musculoskeletal system.

The prosthetic joint or a prosthetic component of the joint can alsohave a number of sensors for generating measurement data related to theinstallation. For example, joint position or prosthetic componentloading can be monitored in surgery or long-term. A result of themonitoring could be that an exercise regimen could be prescribed toimprove the range of motion. Similarly, balance, loading, alignment, orjoint position could be monitored or data stored to study kinematics ofthe joint or provide a kinetic assessment of the joint.

FIG. 1 is an illustration of a leg 10 in accordance with an exampleembodiment. Leg 10 can be a right or left leg. Leg 10 comprises a femur12 and a tibia 14. A dashed line 16 illustrates a mechanical axis of leg10. The mechanical axis of leg 10 comprises dashed line 16 drawn througha center of a femoral head 28 to a center of ankle joint 18. Dashed line16 aligns through a center of a knee joint at approximately the medialtibial spine. The knee joint comprises lateral and medial articularsurfaces that support leg movement. Alignment of leg 10 to themechanical axis minimizes wear on articular surfaces of a prostheticknee joint and reduces mechanical stress on the wear surfaces.Similarly, alignment to the mechanical axis of leg 10 reduces stress onthe prosthetic components coupled to femur 12 and tibia 14. Alignment ofthe knee joint further includes balancing between the lateral and medialcompartments of the knee joint.

A dashed line 22 is a vertical axis that is drawn relative to themechanical axis and an anatomical axis. A dashed line 24 is a horizontalaxis that is perpendicular to vertical axis 22. The horizontal axis isshown drawn between a distal end of femur 12 and a proximal end of tibia14. The vertical axis aligns with the pubic symphysis which is a midlinecartilaginous joint in proximity to a pelvic region. The anatomical axisis illustrated by dashed line 20. The anatomical axis is not a straightline as it traverses an intramedullary canal of femur 12 and anintramedullary canal of tibia 14. The mechanical axis and the anatomicalaxis are the same from the knee joint to the center of the ankle of theleg. Both the mechanical axis and the anatomical axis differ from thevertical axis.

The femur 12 and tibia 14 can be misaligned to the mechanical axis ofthe leg. In an aligned leg, the mechanical axis forms an angle ofapproximately 3 degrees with the vertical axis. Similarly, in an alignedleg, femur 12 of the anatomical axis forms a 5-7 degree angle with themechanical axis. Ideally, a surgeon installs prosthetic components ofthe knee joint aligned to the mechanical axis of the leg to optimizereliability and performance of the knee joint. The alignment process caninclude measurement of leg misalignment and compensation to keepalignment of the leg to the mechanical axis within a predeterminedrange. Typically, the predetermined range is determined by a prostheticcomponent manufacturer based on clinical evidence that supportsreliability and performance of the joint when misalignment is keptwithin the predetermined range. Mechanical jigs have been used tomeasure leg alignment in the operating room. The mechanical jigs can becumbersome, take time to set up, and can be inaccurate. One issue withmechanical jigs is that the center of the femoral head is not availablefor direct measurement by the jigs. In the case of a leg deformity asurgeon may require an alignment offset from the mechanical axis. Ingeneral, leg alignment can be adjusted through bone cuts, prostheticcomponent rotation, ligament tensioning, prosthetic component shimming,and other techniques during a trial installation. In one embodiment, areal-time alignment measurement system uses a tri-axial gyroscope orthree separate gyroscopes to provide alignment measurement data duringtrialing of prosthetic components. The alignment measurement data can beused to verify alignment or to support change that places the leg inalignment.

FIG. 2 is an exploded view of a prosthetic knee joint 40 in accordancewith an example embodiment configured to measure alignment of a leg. Theprosthetic knee joint comprises a femoral prosthetic component 48coupled to a distal end of a femur 42, an insert 58, and a tibialprosthetic component 50 coupled to a proximal end of a tibia 44. Atri-axial gyroscope 62 is coupled to the knee joint to support real-timealignment measurement. In one embodiment, tri-axial gyroscope 62 iscoupled to tibia 44. Tri-axial gyroscope 62 comprises three gyroscopeswhere a first, second, and third gyroscope is respectively aligned to X,Y, and Z axes. Each gyroscope measures an angular velocity correspondingto an axis as indicated on the diagram. Alternatively, three separategyroscopes can also be used to measure leg alignment each gyroscoperespectively aligned to a corresponding axis as shown.

The proximal end of tibia 44 has a prepared bone surface 46. Preparedbone surface 46 of tibia 44 is cut relative to a reference. For example,the proximal end of tibia 44 can be cut relative to the transepicondylaraxis. Alternatively, there are other references that can also be used.Bone cuts to the femur and tibia can also be made referenced to thevertical axis, mechanical axis, or anatomical axis. Prepared bonesurface 46 can have a medial-lateral slope, anterior-posterior slope ora compound slope that supports accurate leg movement and proper rotationof femoral component 48 over a range of motion.

Tibial prosthetic component 50 includes an upper surface 54 and a bottomsurface 56. In one embodiment, upper surface 54 is a major surface of atibial tray. The tibial tray supports and retains insert 58 to tibialprosthetic component 50. Tibial prosthetic component 50 can have one ormore retaining features for coupling to prepared bone surface 46. In oneembodiment, tibial prosthetic component 50 has a keel 52 that insertsinto an opening 66 drilled into tibia 44. Opening 66 defines a locationof tibial prosthetic component 50 on prepared bone surface 46. Keel 52positions, retains, and strengthens coupling of tibial prostheticcomponent 50 to tibia 44. Tibial prosthetic component 50 can be rotatedfrom a reference position. In one embodiment, a position of tibialprosthetic component 50 on tibia 44 is referenced to a medial third ofthe tibia tubercle. Rotation of tibial prosthetic component 50 from thisreference position can be measured and provided to the alignmentmeasurement system. For example, rotation can be used to affect movementof the patella to femoral prosthetic component 48. Rotation of tibialprosthetic component 50 can also be used to affect alignment, balance,and contact point of femoral prosthetic component 48 to insert 50. Oncethe position of tibial prosthetic component 50 is determined bottomsurface 56 of tibial prosthetic component 50 can be coupled to preparedbone surface 46 to further retain tibial prosthetic component 50 totibia 44. Coupling of tibial prosthetic component 50 to tibia 44typically comprises a mechanical attachment, an adhesive, or cement.

Bottom surface 56 of tibial prosthetic component 50 couples to preparedbone surface 46. In one embodiment, bottom surface 56 is approximatelyparallel to prepared bone surface 46. Similarly, upper surface 54 oftibia prosthetic component 50 is parallel to bottom surface 56 orprepared bone surface 46. A surface 60 of insert 58 couples to uppersurface 54 of tibial prosthetic component 50. Insert 58 can have one ormore retaining features that couple to tibial prosthetic component 50.Surface 60 of insert 58 is parallel to upper surface 54 of tibialprosthetic component 50.

In one embodiment, tri-axial gyroscope 62 is a MEMs (micro-electromechanical) integrated circuit. The form factor of a MEMs gyroscopeintegrated circuit supports placement in a prosthetic component orcoupling to a prosthetic component to measure alignment of themuscular-skeletal system. A MEMs gyroscope is a solid state deviceformed using a photolithographic process. The MEMs gyroscope has a formfactor that supports placement within a prosthetic component or a modulethat can be coupled to a bone surface. In one embodiment, MEMs gyroscopehas a resonating mass that shifts when angular velocity changes andoutputs a signal corresponding to the angular velocity change. MEMsgyroscopes can provide an analog or digital output. In one embodiment,measurement data from tri-axial gyroscope 62 is transmitted to acomputer 43 configured to process and display alignment information ofthe leg. Typically, tri-axial gyroscope 62 includes a mounting surface.The mounting surface can correspond to a plane of two of the axes oftri-axial gyroscope 62. In one embodiment, the X-Y plane of tri-axialgyroscope 62 is placed parallel to prepared bone surface 46 of tibia 44and corresponding parallel surfaces of tibial prosthetic component 50and insert 58. In one embodiment, tri-axial gyroscope 62 is placed in atrial insert. The trial insert is used to support installation of aprosthetic knee joint. The trial insert with tri-axial gyroscope 62 canmeasure alignment of the leg and support changes or modifications priorto final installation to ensure alignment is within a predeterminedrange for optimal performance and reliability. The trial insert can alsoinclude other sensors to provide measurement data on other parameters inproximity to the leg or to support installation of the prostheticcomponents. Tri-axial gyroscope 62 can also be placed in otherprosthetic components or a module. For example, tri-axial gyroscope 62can be placed in a final insert or a final tibial prosthetic componentto perform alignment measurements long-term or monitor changes inalignment. As disclosed herein above, the position of tibial prostheticcomponent 50 can be aligned or referenced to the medial third of thetibia tubercle. The orientation of insert 58 corresponds to the positionof tibial prosthetic component 50. Insert 58 incorporating tri-axialgyroscope 62 is placed having the X-axis aligned to ananterior-posterior direction of insert 58 and the Y-axis aligned to themedial-lateral direction of insert 58.

FIG. 3 is an illustration of a prosthetic component incorporating atri-axial gyroscope 82 in accordance with an example embodiment. Ingeneral, the tri-axial gyroscope 82 can be housed in a prostheticcomponent 70 or coupled to the muscular-skeletal system to measurealignment. Tri-axial gyroscope 82 can measure alignment of themuscular-skeletal system or measure bone position. Tri-axial gyroscope82 can have a predetermined orientation referenced to the prostheticcomponent. The prosthetic component can be a trialing device that is atemporary device used during installation for measuring parameters anddetermining appropriate fit of the prosthetic joint. The prostheticcomponent can also be a permanent prosthetic component that monitors ormeasures alignment long-term. For example, changes in alignment overtime can indicate incorrect loading on the articular surfaces thatlong-term could accelerate wear if not corrected. Although tri-axialgyroscope 82 is placed in a knee joint it is not limited to kneeprosthetic components and can be applied similarly to other parts of theanatomy such as but not limited to the muscular-skeletal system, hip,shoulder, spine, ankle, elbow, wrist, fingers, toes, and wrist.Similarly, tri-axial gyroscope 82 can be placed in other knee componentssuch as a patellar button, tibial prosthetic component, or femoralprosthetic component to support alignment measurement or othermeasurements.

In one embodiment, insert 70 comprises a support structure 72 havingarticular surfaces 74 and a support structure 76. Support structures 72and 76 couple together to form a housing. The housing includes at leastone cavity for electronic circuitry and sensors. In one embodiment, aperipheral surface of support structure 72 couples to a peripheralsurface of support structure 76. The surfaces can be coupled togethervia an adhesive that seals the cavity from the external environment. Theinterior and exterior of insert 70 can be sterilized and stored in apackage prior to use. Support structures 72 and 76 comprise abio-compatible polymer such as polycarbonate, PEEK, or ultrahighmolecular weight polyethylene. The selected polymer can support loadingapplied by the muscular-skeletal system while providing a low frictionsurface for joint movement and reduced wear.

A measurement system comprises tri-axial gyroscope 82, sensors,electronic circuitry 78, a power source 88, and a remote system.Tri-axial gyroscope 82, sensors, electronic circuitry 78, and powersource 88 are housed in insert 70. The remote system is placed inproximity to insert 70. For example, the remote system can be placed inan operating room in a location that allows the surgical team to viewmeasurement data provided by the sensors and tri-axial gyroscope 82. Theremote system receives measurement data from the sensors and tri-axialgyroscope 82 via wired connection or wireless transmission. Typically,wireless transmission is short range, usually less than 10 meters andcan be encrypted for security. The remote system can comprise a computerwith a display to receive and process measurement data from insert 70.The computer can include software programs to support calculation andvisualization of the measurement data. In one embodiment, themeasurement data can be displayed to the surgeon in real-time allowingchanges to be made based on the quantitative measurements.Alternatively, the remote system can be a microprocessor based devicecapable of running software such as a smart phone or handheld devicethat allows a patient to review measurement data transmitted from theprosthetic component.

Insert 70 couples to a tibial prosthetic component 90. Tibial prostheticcomponent 90 couples to a tibia and includes a tibial tray 92 thatretains insert 70. Tibial tray 92 includes a surface 94 to which bottomsurface 86 of structure 76 couples. Articular surfaces 74 couple tocondyles of a femoral prosthetic component to support movement of theknee joint and the leg. Load sensors 80 can be placed underlyingarticular surfaces 74. The measurement system can measure load andposition of load applied to articular surfaces 74. The load applied toarticular surfaces 74 is distributed to a bottom surface 86 of supportstructure 76 that couples to a tibial prosthetic component 90. Thesurface area of bottom surface 86 is greater in area than the condylecontact area of the femoral prosthetic component to articular surfaces74. The measurement system also includes tri-axial gyroscope 82 formeasuring alignment of a leg relative to a mechanical axis of the leg.The tri-axial gyroscope comprises three gyroscopes. A first gyroscopehas a rotational axis aligned in an anterior-posterior direction ofinsert 70 corresponding to an axis X. A second gyroscope has arotational axis aligned in a medial-lateral direction of insert 70corresponding to an axis Y. A third gyroscope has a rotational axisperpendicular to an X-Y plane corresponding to an axis Z.

Electronic circuitry 78 can be housed in the prosthetic component withtri-axial gyroscope 82 aligned as stated above or in anotherpredetermined alignment. Alternatively, three separate gyroscopes can beused and aligned in the predetermined alignment. As mentioned tri-axialgyroscope 82 is a small form factor device that allows placement withinthe prosthetic component or device that couples to the muscular-skeletalsystem. The sensors can measure a parameter of the musculoskeletalsystem or measure a parameter in proximity to insert 70.

Electronic circuitry 78 is mounted on a printed circuit 84 that iscentrally mounted in the cavity of insert 70. Electronic circuitry 78 ismounted in an area of insert 70 that has little or no joint loading forreliability. Load sensors 80 couple to electronic circuitry 78 andunderlie articular surfaces 74. In one embodiment, load sensors 80 andelectronic circuitry 78 are coupled to a flexible and unitary printedcircuit board. In one embodiment, load sensors 80 can be integrated intothe printed circuit board to simplify assembly, improve reliability, andincrease performance of the measurement system. Three or more loadsensors 80 are used measure a position where the load is applied onarticular surfaces 74. A tri-axial gyroscope 82 is mounted to printedcircuit board 84 and couples to electronic circuitry 78. Tri-axialgyroscope 82 is mounted such that the three gyroscopes are oriented inrelation to the prosthetic component. In one embodiment, the X-Y planeof tri-axial gyroscope 82 is parallel to bottom surface 86 of insert 70and surface 94 of tibial prosthetic component 90.

Electronic circuitry 78 and tri-axial gyroscope 82 are isolated from anexternal environment when support structure 72 is coupled to supportstructure 76 of FIG. 3 . Electronic circuitry 78 can include a powersource 88, passive components, power regulation, power managementcircuitry, conversion circuitry, digital logic, analog circuitry,microprocessors, microcontrollers, digital signal processors, memory,ASICs, interface circuitry, or communication circuitry. In oneembodiment, tri-axial gyroscope 82 provides measurement data inreal-time to a computer via radio frequency wireless transmission.

FIG. 4 is an illustration of a gyroscope 100 in accordance with anexample embodiment. Gyroscope 100 is a tri-axial gyroscope where a firstgyroscope is oriented to an X-axis, a second gyroscope is oriented to aY-axis, and a third gyroscope is oriented to a Z-axis. Gyroscope 100 isa dynamic device that produces an output as the device is moved.Gyroscope 100 does not produce an output under static conditions. In oneembodiment, gyroscope 100 is a solid state MEMS (MicroelectromechanicalSystem). A MEMS gyroscope has a small form factor suitable for placementwithin a prosthetic component. A MEMS gyroscope is formed byphotolithographic processes on a silicon substrate. A single MEMSgyroscope of gyroscope 100 comprises a resonating mass that vibratesabout its axis of symmetry. Movement of gyroscope 100 affects theresonating mass. A rotation about the axis results in a Coriolis forcebeing generated that is sensed or detected. The force measurementconversion from mechanical to electrical is built into the device. Inone embodiment, a gyroscope includes a capacitor sensing structure. Asthe resonating mass moves out of plane due to movement of the gyroscopea corresponding change is produced in the capacitor. Thus, themechanical movement is converted to an electrical parameter. Electroniccircuitry can be coupled to gyroscope 100 to monitor the capacitanceoutput or convert the capacitance value to an analog signal or a digitalsignal.

In general, gyroscope 100 is coupled to a bone of the musculoskeletalsystem. In the example, gyroscope 100 is coupled to a proximal end of atibia. Gyroscope 100 can be placed in an insert or a tibial prostheticcomponent to measure alignment relative to the mechanical axis of theleg. Angles related to alignment of the leg can be measured by movingthe leg through a predetermined movement. In one embodiment, a first legmovement and a second leg movement are performed with the measurementdata of gyroscope 100 being provided to a computer. The computer willhave software that can calculate one or more angles using themeasurement data. The angles can be provided to a surgeon in real-timein the operating room to verify a correct leg alignment or to indicatecorrections required to put the leg in correct alignment duringinstallation of a knee joint. Similarly, gyroscope 100 could be used ina permanent prosthetic component to measure leg alignment or legposition by providing the measurement data to a microprocessor or DSPbased device such as a smartphone.

Gyroscope 100 measures angular velocity related to the three axes X, Y,and Z when coupled to the tibia as shown in FIG. 2 . In one embodiment,the three axes have a predetermined alignment relative to the prostheticcomponent in which it is placed. In the example, the leg or knee jointis rotated less than 360 degrees and the movement is being performed bythe surgeon at a relatively slow speed. Thus, gyroscope 100 can detectsmall changes corresponding to misalignment of the leg to a mechanicalaxis. Gyroscope 100 is not affected by linear acceleration or linearvelocity and only measures angular velocity. Acceleration and velocityare linked and therefore angular velocity is altered by angularacceleration. In one embodiment, gyroscope 100 has a range +−2000degrees/second and an output rate of 20-128 Hertz. In the disclosedapplication, the angular velocity being measured is much less than themeasurement range of the gyroscope. Reducing the measurement range willtypically improve the sensitivity of gyroscope 100 for the alignmentmeasurement. In one embodiment, gyroscope 100 and ancillary electroniccircuitry used to measurement alignment of the muscular skeletal ispowered by a power source. The power source can be a battery, capacitor,inductor, or other energy storage device that can last for the entireinstallation of the prosthetic joint. In one embodiment, thetrial-insert is a single use device and is disposed of after surgery.Gyroscope 100 can be operated at the lower end of the output rate tomaximize battery life without impact to the accuracy of themeasurements. In one embodiment, a digital interface is used withgyroscope 100 to support coupling with control logic, a microcontroller,ASIC, microprocessor, or digital signal processor.

It should be noted that accelerometers have been used to measuremuscular-skeletal alignment and have been found to not work under allcircumstances. For example, using an accelerometer under a staticmeasurement it is not possible to determine a three dimensionalorientation from a single gravity reference. Also, under dynamicconditions, it is not possible to separate acceleration due to gravityfrom an applied acceleration due to an external force. Theabove-mentioned issues when using an accelerometer for muscular-skeletalalignment can manifest in producing error when one axis is aligned withgravity or the inability to distinguish roll and yaw.

FIG. 5 is a block diagram 110 of gyroscope 100 and electronic circuitryin accordance with an example embodiment. Gyroscope 100 is a MEMStri-axial gyroscope as described in FIG. 4 . The axes of gyroscope 100are referenced to a prosthetic component or a bone surface to support analignment measurement of the musculoskeletal system. In one embodiment,gyroscope 100 includes a digital interface that uses SPI or I2Ccommunication protocols. Either interface can work at the low samplerequired for the alignment application. Electronic circuitry comprisescontrol logic 114, memory 116, and transceiver 118. A computer 120receives measurement data from gyroscope 100. In one embodiment, theelectronic circuitry is housed in a prosthetic component.

Control logic 114 can comprise one or more of an FPGA, microcontroller,microprocessor, microprocessor, digital signal processor, or digitallogic. In general, control logic 114 is configured to control ameasurement process or measurement sequence to generate quantitativemeasurement data that supports calculation of muscular-skeletalalignment using gyroscope 100. Control logic 114 is operatively coupledto gyroscope 100. Control logic 114 includes one or more control signalsthat support the measurement process. Memory 116 is coupled to controllogic 114. Memory 116 can include a software program to generatemeasurement data related to alignment of the muscular-skeletal system.The software program can be executed by control logic 114. Control logic114 further includes input/output circuitry coupled to gyroscope 100configured to receive measurement data. Control logic 114 can store themeasurement data in memory 116. Transceiver 118 is coupled toinput/output circuitry of control logic 114. Transceiver 118 is used toreceive or transmit information or data.

Computer 120 is coupled to the electronic circuitry. Computer 120 can becoupled via a wired or wireless coupling. In one embodiment, computer120 is placed outside a sterile field of an operating room. A display ofcomputer 120 is placed in view of a surgical team for receivingmuscular-skeletal alignment information. Computer 120 receivesmeasurement data from the electronic circuitry and gyroscope 100.Computer 120 can also transmit information to the electronic circuitrythat initiates or supports the measurement process. Computer 120 caninclude software to process the measurement data from gyroscope 100,perform calculations, calculate alignment, provide a workflow, anddisplay information. For example, computer 120 can provide a visualimage of a femur and tibia misaligned to the mechanical axis. Computer120 could also produce one or more different workflows to correct themisalignment based on the quantitative measurement data.

FIG. 6 is an illustration of angles measured by a gyroscope coupled to aproximal end of a tibia 150 in accordance with an example embodiment. Ingeneral, a surgeon prepares bone surfaces to receive a prostheticcomponent. The bone cuts on the prepared surface of a bone can affecthow the bone geometrically interacts with another bone or prostheticcomponent. In the example, a total knee arthroplasty (TKA) replaces afaulty knee joint with a prosthetic knee joint. The alignment of theprosthetic knee components to one another and to the femur and tibiaaffects leg performance and reliability. Misalignment affects legkinematics, joint wear, or could lead to a catastrophic issue requiringjoint replacement. Thus, accurate quantitative measurement of thealignment prior to installation, during installation, or postinstallation of the prosthetic components will improve both short-termand long term results of the patient. Furthermore, the quantitativemeasurement data can be used by manufacturers of prosthetic componentsto assess and improve the designs.

Referring to FIG. 14 , a knee joint 310 comprises a femoral prostheticcomponent 312, an insert 314, and a tibial prosthetic component 316.Femoral prosthetic component 312 is coupled to prepared bone surfaces ona distal end of a femur 148. Tibial prosthetic component 316 is coupledto a prepared bone surface on a proximal end of a tibia 150. Insert 314couples to tibial prosthetic component 316 and includes articularsurfaces to support movement of the leg. A tri-axial gyroscope is partof a measurement system that provides quantitative measurement datarelated to alignment in real-time. In the example, the tri-axialgyroscope is in insert 314. The gyroscope is in a predeterminedorientation within insert 314. The measurement data output by thetri-axial gyroscope is used in conjunction with the leg geometry tocalculate angles that can be used to verify that the leg is inalignment.

Referring back to FIG. 6 , geometrically a triangle can be formed aroundthe leg that relate to the alignment of the leg. A line 140 represents aline drawn from a center 142 of a femoral head to a center 146 of anankle and is indicated by the letter C. A line 152 is drawn from center142 of the femoral head to a center 144 of a knee joint. Line 152 isalso identified by a letter B. A line 154 is drawn from center 144 ofthe knee joint to center 146 of the ankle. Line 154 is also identifiedby a letter A and corresponds to tibia 150. The triangle comprises lines140, 152, and 154. In one embodiment, the center of the knee joint canbe related to a bone landmark such as the medial tibial spine. Thetriangle comprises three angles that can be measured using measurementdata from a tri-axial gyroscope coupled to tibia 150 in conjunction withthe lengths of line 140, line 152, and line 154.

Angles related to the frontal plane of a total knee arthroplasty can becalculated using measurement data from a tri-axial gyroscope coupled totibia 150 similar to that disclosed in FIG. 2 or within a prostheticcomponent as disclosed in FIG. 3 . An angle 156 that is identified by aletter α corresponds to a hip angle. The hip angle is an angle formed byline 140 and line 152 having an intersection at center 142 of thefemoral head. An angle 160 that is identified by a letter γ is a kneeangle. The knee angle is an angle formed by line 152 and line 154 havingan intersection at the center of the knee joint. An angle 158 isidentified by a letter β is an ankle angle. The ankle angle is an angleformed by line 140 and line 154 having an intersection at the center ofthe ankle. In particular, the knee angle or angle 160 in the sagittaland frontal planes is used to support alignment of the prostheticcomponents. In one embodiment, the length of line B is known. Similarly,the length of line A is known. Measurement of A and B is disclosedherein below. The measurement of line 152 corresponding to femur 148 andline 154 corresponding to tibia 150 will be provided in more detailherein below. The Law of Cosines equation is used to solve for thelength of line 140 corresponding to the distance from the center 142 ofthe femoral head of femur 148 to the center 146 of the ankle. The Law ofCosines is represented in equation 1 listed below.A ² =B ² +C ²−2BC cos(α_(Frontal))  Equation 1:

A measurement system using a tri-axial gyroscope is coupled to tibia150. In the example, tri-axial gyroscope 62 of FIG. 2 has the axesaligned as indicated to tibia 44 of FIG. 2 . The angle α_(Frontal) canbe measured by moving the leg through a first movement using measurementdata from the tri-axial gyroscope 62. The angle α_(Frontal) is a frontalhip angle that is measured from measurement data generated by thetri-axial gyroscope during the first movement. In general, the firstmovement is a rotation of the leg that may produce angular velocities oneach axis. Referring to FIG. 7 , the first movement is illustrated inaccordance with an example embodiment. In the example, the right leg 176is used to show the first movement. The motion can be performed oneither leg in a similar manner. Leg 176 is placed in full extension. Inone embodiment, the Z-axis of the tri-axial gyroscope aligns to thejoint line or line 170. The entire leg is rotated about the Z-axis orjoint line of the leg with the leg in full extension. In the firstmovement, the foot, lower leg, and the upper leg are rotated together. Aneutral position corresponding to 0 degrees is indicated by line 170with the patient lying on his or her back with the foot extendingupwards with no torque on the knee or ankle joint. The first movementcomprises rotating the entire leg 176 internally towards line 172 andexternally towards line 174. In one embodiment, leg 176 is rotated 45degrees on either side of the neutral position. The total movement of 90degrees has been found sufficient to provide accurate measurement datafrom the tri-axial gyroscope on each axis. The total movement can bemore or less than 90 degrees. It was found that the rate at which leg176 is rotated affects the accuracy of the measurement more than theamount of total rotation. In one embodiment, leg 176 is rotated betweenlines 172 and 174 at a rate 1.5 radians/second to 8.0 radians/second.The first movement rotation can be further specified as a slow rotationand a fast rotation where the rotation is performed within apredetermined rate range. In one embodiment, a slow rotation of leg 176comprises a rate of 1.5-2.0 radians a second that corresponds toapproximately 86-115 degrees/second. A fast rotation of leg 176comprises a rate of 6.0-8.0 radians/second that corresponds toapproximately 344-458 degrees/second. Maintaining movement of leg 176within these ranges assures the tri-axial MEMs gyroscope will produceaccurate angle measurements related to alignment of the musculoskeletalsystem. The equations herein represent the embodiment where the Z-axisof the tri-axial gyroscope aligns with the mechanical axis of the femurcorresponding to line 152 of FIG. 6 .

Referring back to FIG. 6 the first movement produces quantitativemeasurement data from the tri-axial gyroscope. In one embodiment, thetri-axial gyroscope measurement data is sent to a computer forcalculating one or more parameters. In the example where tri-axialgyroscope is placed in a prosthetic component, the measurement data iswirelessly transmitted to the computer. A sagittal plane knee angle(posterior/anterior slope) is calculated by the computer using thetri-axial gyroscope measurement data related to the X-axis and Z-axisvia direct calculation. A frontal plane angle (varus/valgus) iscalculated by the computer using the tri-axial gyroscope measurementdata related to the Y-axis and Z-axis via the Law of Cosines. Thecomputer directly plots the appropriate gyroscope axes as disclosedabove with respect to one another. In other words, the gyroscope X-axisis plotted versus the Z-axis (sagittal plane) and the computercalculates a line fitted to the measurement data. Similarly, thegyroscope Y-axis is plotted versus the Z-axis (frontal plane) and thecomputer calculates a line fitted to the measurement data. The X-axisversus Z-axis calculated line is used to directly calculate the sagittalknee angle via Equation 2. The Y-axis versus Z-axis calculated line isused in conjunction with Equation 3 to calculate the frontal hip angle.The sagittal knee and frontal hip angles are calculated in the computerusing Equations 2 and 3, respectively.γ_(Sagittal)=arctan(Δω_(X)/Δω_(Z))  Equation 2:α_(Frontal)=arctan(Δω_(Y)/Δω_(Z))  Equation 3:

The angle α_(Frontal) corresponds to the hip angle formed by line 140and line 152 within the triangle formed by the leg. The angleα_(Frontal) is then used in the Law of Cosines to solve for line 140that is also identified as C on FIG. 6 . The length of the joint line orline 140 is solved for in Equation 4 and listed below.C=(2B cos(α_(Frontal))+(2)^(1/2)(2A ² −B ² +B ²cos(2α_(Frontal)))^(1/2))/2  Equation 4:

The computer having calculated the length of frontal joint line lengthor line 140 length uses the calculated length of line 140 to generate afrontal knee angle. The frontal knee angle corresponds to angleγ_(Frontal) that is the knee angle formed by line 152 and line 154within the triangle formed by the leg. The frontal knee angle iscalculated by the computer using Equation 5 listed below.γ_(Frontal)=arccos((A ² +B ² −C ²)/2AB)  Equation 5:

Referring to FIG. 8 , a second movement is illustrated in accordancewith an example embodiment. In the example, the right leg 176 is used toshow the second movement. The motion can be performed on either leg in asimilar manner. The femur of leg 176 is elevated from horizontal. Leg176 can lifted by someone in the surgical team or supported by a fixtureto a stable position. The second movement is a rotation of the tibiaabout the femur or a kicking motion. Elevating the femur allows thetibia to move freely from flexion 180 to extension 178. In oneembodiment, leg 176 is rotated between flexion 180 and extension 178 ata rate 1.5 radians/second to 4.0 radians/second. The second movementrotation can be further specified as a slow rotation and a fast rotationwhere the rotation is performed within a predetermined rate range. Inone embodiment, a slow rotation of leg 176 in the second movementcomprises a rate of 1.5-2.0 radians a second that corresponds toapproximately 86-115 degrees/second. A fast rotation of leg 176 in thesecond movement comprises a rate of approximately 4.0 radians/secondthat corresponds to approximately 229 degrees/second.

Referring back to FIG. 6 the second movement produces quantitativemeasurement data from the tri-axial gyroscope. In one embodiment, thetri-axial gyroscope measurement data is sent to a computer forcalculating one or more parameters. In the example where the tri-axialgyroscope is placed in a prosthetic component, the measurement data fromthe second movement is wirelessly transmitted to the computer. A directcalculation of an angle is possible by comparing the appropriate axes.For example, there is no triangle formed to use the Law of Cosines whenlooking at the transverse plane of the tibial tray through the secondrotation. The computer can plot the X-axis against the Y-axis and fit aline to that the measurement data from the tri-axial gyroscopecorresponding to the second movement of the leg. The calculated linefrom the X-axis against the Y-axis is used in Equation 6 to calculatethe knee transverse angle. The angle is calculated using equation 6 inthe computer and calculating the arc tangent of 1 divided by the slopeof the line related to the knee tibial transverse angle or the slope ofthe line related to the knee tibial frontal angle.γ_(Transverse)=arctan(Δω_(X)/Δω_(Y))  Equation 6:

FIG. 9 is an illustration of a patient in a sitting position inaccordance with an example embodiment. As disclosed herein above thelength of a femur and a length of a tibia are needed to calculatealignment of the leg. As mentioned previously, images of the femur ortibia can be measured and scaled to determine length of each bone. Inparticular, a center of a femoral head and the center of the knee can beidentified in an image. Similarly, the center of the knee to the centerof the ankle can be identified in an image. In one embodiment, theimages can be scanned into the computer or digital images can beprovided to the computer. The computer can then identify bone landmarksrelated to measuring the length of a bone of the musculoskeletal system,measure the length of a bone image, and scale the bone image to providea length for the bone.

Alternatively, a measurement of each bone can be made prior to asurgery. The measurement can be made using a measuring device such as atape measure or ruler. In the example, a femur 184 and a tibia 182 aremeasured. Although the measurements cannot be exact, it has been foundthat the measurements as described herein below do not impact thecalculations significantly and support alignment measurement of themusculoskeletal system within a tolerance that provides effectiveinstallation of prosthetic components. The patient is placed on a chairor table in a sitting position. An approximate length of tibia 182 canbe measured from the bottom of the foot to a lateral condyle of tibia182. The lateral condyle can be identified by moving the leg or tibia182 in flexion as the patient is in the sitting position and tracing thecondyles of the femur with the fingers to tibia 182. On the lateral sideof the knee the femoral condyle will contact the lateral condyle oftibia 182 or articular surface of the tibia 182. A ruler can be placedadjacent to the leg to measure from the bottom of the foot to thelateral condyle.

Similarly, the length of femur 184 can be measured. In one embodiment,an approximate length of the femur can be measured from the greatertrochanter at a proximal end of the femur to the femoral epicondyle. Thegreater trochanter can be found by tracing the pelvic region of the legto femur 184 until a bony protrusion (e.g. greater trochanter) isidentified. The patient can move the leg in a manner that moves femur184 to verify corresponding movement of the greater trochanter. Thefemoral epicondyle can be found in a similar manner. The femoral lateralepicondyle is a bony projection near the distal end of femur 184 whereligaments or tendons are attached. The femoral lateral epicondyle can bedetected through feel of the bony projection. A ruler can be placedadjacent the leg to measure from the greater trochanter to the femorallateral epicondyle to approximately measure the length of femur 184.

FIG. 10 is an illustration of a clinical flow to measure alignment of aleg in accordance with an example embodiment. A method of alignmentusing a measurement system is disclosed. The method can be practicedwith more or less steps and is not limited to the order of steps shown.The method is not limited to the knee example but can be used for hip,knee, shoulder, ankle, elbow, spine, hand, wrist, foot, bone, andmusculoskeletal system. The components listed in the method can bereferred to and are disclosed in FIGS. 2 and 3 .

In a step 192, a length of a tibia and a femur are measured. Asdisclosed herein above, the tibia and the femur can be measured prior tosurgery to install a prosthetic knee joint. The tibia and the femur canbe measured using a ruler or other measurement device by locating andidentifying bone landmarks of the tibia or the femur and measuring thedistance between the bone landmarks. A length of a tibia can beapproximated by measuring from a bottom of a foot to a lateral condyle.A length of a femur can be approximated by measuring from a greatertrochanter to a femoral epicondyle. Alternatively, images of the tibiaand the femur can be provided to a computer. The computer can identifybone features and landmarks, measure the length of the bone, and scalethe measurement to a bone length.

The alignment system comprises three gyroscopes, electronic circuitry,and a computer. The three gyroscopes can also be housed in a singlepackage as a tri-axial gyroscope. In one embodiment, the gyroscope andelectronic circuitry are housed in a trialing prosthetic component. Thetrialing prosthetic component can further include one or more sensorsfor measuring a parameter of the muscular-skeletal system and a powersource. The trialing prosthetic component can be single use device andis disposed of after being used in the operating room. Measurement datafrom the gyroscope can be wirelessly transmitted to the computer. Thecomputer can perform calculations and execute software to measurealignment in real-time and provide alignment information and data in theoperating room. The alignment system can be used in a similar fashion toprovide measurement data to a computer if the gyroscope is placed in apermanent prosthetic component to monitor alignment long-term. In theexample where the tibia and femur are measured, the length of the tibiaand the length of the femur are entered into to the computer.

In a step 194, surgical cuts or bone cuts are made to the tibia toreceive a tibial prosthetic component. In one embodiment, the gyroscopecouples to a prepared bone of the proximal end of the tibia of a leg.The tibial prosthetic component comprises a tibial tray and a keel. Thekeel of the tibial prosthetic component is inserted into the tibialmedullary canal to support, stabilize, and position the tibialprosthetic component to the prepared bone surface. Installing the tibialprosthetic component to the proximal end of the tibia couples a bottomsurface of the tibial tray to the prepared bone surface. In oneembodiment, the tibial prosthetic component is aligned to or relative toa bone landmark of the tibia. The tibial prosthetic component istypically glued to the tibia.

In a step 196, an insert is placed in the tibial tray of the tibialprosthetic component. In one embodiment, a tri-axial gyroscope and theelectronic circuitry are housed in a prosthetic component. In theexample, the tri-axial gyroscope, electronic circuitry, and power sourceare housed in an insert. One plane of the tri-axial gyroscope can beparallel to a prepared bone surface of the proximal end of the tibia, asurface of the tibial tray, or a bottom surface of the insert. A firstaxis of the tri-axial gyroscope can be aligned to the anterio-posteriodirection of the insert. A second axis of the tri-axial gyroscope can bealigned to the medial-lateral direction of the insert. A third axis ofthe tri-axial gyroscope can be perpendicular to the plane of the firstand second axes. Thus, the tri-axial gyroscope can have a predeterminedalignment with the insert, the tibial prosthetic component, and thetibia that relates to the anatomy of the leg and the alignment of theleg.

In a step 198, a first movement is performed. The gyroscope responds tomovement and provides angular velocities related to each axis. In oneembodiment, the gyroscope measurement data related to the first movementis used to measure a system sagittal angle and a system frontal angle.The leg is placed in extension for the first movement. The leg is thenrotated about the hip and an ankle. The electronic circuitry of theinsert transmits angular velocity measurement data related to each axisfrom the tri-axial gyroscope as the leg moves through the firstmovement. The first movement can be repeated one or more times. In oneembodiment, the leg is rotated 45 degrees on either side of a neutral orzero degree position. Furthermore, the leg has to be rotated above apredetermined rate. A slow rotation of the leg comprises a rate of1.5-2.0 radians a second that corresponds to approximately 86 -115degrees/second. A fast rotation of the leg comprises a rate of 6.0-8.0radians/second that corresponds to approximately 344-458 degrees/second.The measurement data is sent to and received by a computer. The computerincludes a software program that uses the measurement data from thegyroscope to calculate alignment. The computer calculates a systemsagittal angle and a system frontal angle related to leg alignment fromthe measurement data related to the first movement of the leg. Othercalculations that are performed by the computer are disclosed in detailin FIG. 6 herein above.

In a step 200, a second movement is performed. The gyroscope responds tomovement and provides angular velocities related to each axis. In oneembodiment, the gyroscope measurement data related to the secondmovement is used to measure a tibial frontal angle and a tibialtransverse angle. In the second movement the patient is in a supineposition with the femur elevated. The second movement comprises rotatingthe tibia about a femur. This movement is similar to a kicking motionwhere the femur is stationary in the elevated position and the tibiamoves from flexion to extension. The electronic circuitry of the inserttransmits angular velocity measurement data related to each axis fromthe gyroscope as the leg moves through the second movement. The secondmovement can be repeated one or more times. The rotation of the tibiaabout the femur has to be rotated above a predetermined rate. A slowrotation of the leg in the second movement comprises a rate of 1.5-2.0radians a second that corresponds to approximately 86 -115degrees/second. A fast rotation of the leg in the second movementcomprises a rate of approximately 4.0 radians/second that corresponds toapproximately 229 degrees/second. The measurement data is sent to andreceived by a computer. The computer includes a software program thatuses the measurement data from the gyroscope to calculate alignment. Thecomputer calculates the tibial frontal angle and the tibial transverseangle related to leg alignment from the measurement data related to thesecond movement of the leg. Other calculations that are performed by thecomputer are disclosed in detail in FIG. 6 herein above.

In a step 202, a read out 3D orientation angles are provided inreal-time. In one embodiment, the computer is coupled to a display thatcan be viewed by a surgical team in the operating room. Measurement datafrom the three gyroscopes or a tri-axial gyroscope has been provided tothe computer as the leg undergoes at least two different movements. Oneor more metrics are provided on the display to the surgical team relatedto the alignment of the leg after the first movement or the secondmovement is completed. The system sagittal angle, the system frontalangle, the tibial frontal angle or a tibial transverse angle can bedisplayed on the display. In one embodiment, the 3D orientation anglesare the system sagittal angle for the sagittal plane, the system frontalangle minus the tibial frontal angle for the frontal plane, and thetibial transverse angle for the transverse plane. The computer couldalso generate other measurement data related to alignment from the datacollected from the gyroscopes and other sensors. The computer can alsoprovide visual, audible, or haptic feedback to support the quantitativemeasurement data. For example, a femur, prosthetic knee joint, and tibiacan be displayed on the screen in a manner that illustrates the measuredangles. The computer can simulate movement of the leg and providealignment information over a range of motion. The computer can alsoprovide one or more workflows that can be implemented to bring the leginto better alignment using the measurement data. The workflows wouldcomprise steps to alter the alignment such as bone cuts, ligamenttensioning, or shimming.

FIG. 11 is an illustration of a software flow 220 to measure alignmentof a leg in accordance with an example embodiment. A method of alignmentusing a measurement system is disclosed. The method can be practicedwith more or less steps and is not limited to the order of steps shown.The method is not limited to the knee example but can be used for hip,knee, shoulder, ankle, elbow, spine, hand, wrist, foot, bone, andmusculoskeletal system. The components listed in the method can bereferred to and are disclosed in FIGS. 2 and 3 .

A trial measurement system comprises a prosthetic component and acomputer. In one embodiment, the trial measurement system can measureleg alignment. The prosthetic component includes a tri-axial gyroscope,electronic circuitry, and a power source. The electronic circuitrycouples to the tri-axial gyroscope, controls a measurement process, andtransmits measurement data from the tri-axial gyroscope. The prostheticcomponent has an internal cavity that houses the tri-axial gyroscope,electronic circuitry, and the power source. The internal cavity ishermetically sealed from an external environment. The tri-axialgyroscope is aligned respectively to an anterio-posterio axis and amedial-lateral axis of the prosthetic component. A third axis of thetri-axial gyroscope can be aligned to the joint line when the leg is inextension. In one embodiment, the prosthetic component can be an insertor a tibial prosthetic component. The measurement process is initiatedwhen a leg undergoes at least one movement that supports an alignmentmeasurement of the leg. The computer is configured to receivemeasurement data from the tri-axial gyroscope. In one embodiment, theprosthetic component sends the measurement data wirelessly andencrypted. The computer is in proximity to the prosthetic component toprovide alignment metrics in real-time. The computer is configured tocalculate at least one of a system sagittal angle, a system frontalangle, a tibial frontal angle, or a tibial transverse angle from themeasurement data.

In a step 222, a tibia and a femur length is loaded into a computer. Thetrial measurement system is configured to store the length of the tibiaand the length of the femur in memory on the computer. The computerincludes a software program that uses the tibia and the femur length inat least one calculation. In a step 224, a tri-axial gyroscope in aninsert provides angular velocities related to a first movement of a leg.The tri-axial gyroscope is configured having a predetermined orientationin relation to a tibia of the leg. In one embodiment, the leg is placedin extension for the first movement. The leg is then rotated about thehip and an ankle. In one embodiment, the tri-axial gyroscope isconfigured to measure the leg rotated about the hip and the ankle atgreater than 1.5 radians/second but less than 8.0 radians/second. Thedynamic measurement data generated by the gyroscope is transmitted tothe computer. The software program is executed calculating the systemsagittal angle and system frontal angle. The system sagittal angle andthe system frontal angle can be displayed on a display coupled to thecomputer.

In a step 226, the tri-axial gyroscope in the insert provides angularvelocities of related to a second movement of a leg. In one embodiment,the leg is placed in extension for the first movement. In the secondmovement the patient is in a supine position with the femur elevated.The second movement comprises rotating the tibia about a femur. In oneembodiment, the tri-axial gyroscope is configure to measure the tibiarotated about the femur at greater than 1.5 radians/second but less than4.0 radians/second. The dynamic measurement data generated by thetri-axial gyroscope is transmitted to the computer. The software programis executed calculating the tibial frontal angle and the tibialtransverse angle. The tibial frontal angle and the tibial transverseangle can be displayed on a display coupled to the computer. Examples ofthe equations used in steps 224 and 226 by the computer are disclosed inFIG. 6 herein above.

In a step 228, final 3D orientation angles are calculated. In oneembodiment, the angles are provided in real-time. Measurement data fromthe three gyroscopes or a tri-axial gyroscope is transmitted to thecomputer as the leg undergoes at least a first leg movement and a secondleg movement. One or more metrics are provided on the display to thesurgical team related to the alignment of the leg after the firstmovement or the second movement is completed. A software program isexecuted and the 3D orientation angles are calculated by the computerusing quantitative measurement data from the gyroscopes. In oneembodiment, the system sagittal angle for the sagittal plane, the systemfrontal angle minus the tibial frontal angle for the frontal plane, andthe tibial transverse angle for the transverse plane comprise the 3Dorientation angles that are displayed on a display of the computer. Thecomputer could also generate other measurement data related to alignmentfrom the data collected from the gyroscopes and other sensors. Thecomputer can also provide visual, audible, or haptic feedback to supportthe quantitative measurement data or calculations. For example asoftware program can provide visual feedback related to the 3Dorientation angles by illustrating a femur, prosthetic components, andtibia coupled together with the measured angles. The computer cansimulate movement of the leg and provide alignment information over arange of motion. Visual, audible, or haptic feedback can be used toindicate where alignment is outside a predetermined range. The computercan also provide one or more workflows that can be implemented to bringthe leg into better alignment using the measurement data. The workflowswould comprise steps to alter the alignment such as bone cuts, ligamenttensioning, or shimming.

FIG. 12 is a block diagram of a measurement system or computer inaccordance with an example embodiment. The exemplary diagrammaticrepresentation of a machine, system, or computer in the form of a system250 within which a set of instructions, when executed, may cause themachine to perform any one or more of the methodologies discussed above.In some embodiments, the machine operates as a standalone device. Insome embodiments, the machine may be connected (e.g., using a network)to other machines. In a networked deployment, the machine may operate inthe capacity of a server or a client user machine in server-client usernetwork environment, or as a peer machine in a peer-to-peer (ordistributed) network environment.

The machine may comprise a server computer, a client user computer, apersonal computer (PC), a tablet PC, a laptop computer, a desktopcomputer, a control system, logic circuitry, a sensor system, an ASIC,an integrated circuit, a network router, switch or bridge, or anymachine capable of executing a set of instructions (sequential orotherwise) that specify actions to be taken by that machine. It will beunderstood that a device of the present disclosure includes broadly anyelectronic device that provides voice, video or data communication.Further, while a single machine is illustrated, the term “machine” shallalso be taken to include any collection of machines that individually orjointly execute a set (or multiple sets) of instructions to perform anyone or more of the methodologies discussed herein.

System 250 may include a processor 252 (e.g., a central processing unit(CPU), a graphics processing unit (GPU, or both), a main memory 254 anda static memory 256, which communicate with each other via a bus 258.System 250 may further include a video display unit 260 (e.g., a liquidcrystal display (LCD), a flat panel, a solid state display, or a cathoderay tube (CRT)). System 250 may include an input device 262 (e.g., akeyboard), a cursor control device 262 (e.g., a mouse), a disk driveunit 266, a signal generation device 268 (e.g., a speaker or remotecontrol) and a network interface device 270.

The disk drive unit 266 can be other types of memory such as flashmemory and may include a machine-readable medium 272 on which is storedone or more sets of instructions 274 (e.g., software) embodying any oneor more of the methodologies or functions described herein, includingthose methods illustrated above. Instructions 274 may also reside,completely or at least partially, within the main memory 254, the staticmemory 256, and/or within the processor 252 during execution thereof bythe system 250. Main memory 254 and the processor 252 also mayconstitute machine-readable media.

Dedicated hardware implementations including, but not limited to,application specific integrated circuits, programmable logic arrays andother hardware devices can likewise be constructed to implement themethods described herein. Applications that may include the apparatusand systems of various embodiments broadly include a variety ofelectronic and computer systems. Some embodiments implement functions intwo or more specific interconnected hardware modules or devices withrelated control and data signals communicated between and through themodules, or as portions of an application-specific integrated circuit.Thus, the example system is applicable to software, firmware, andhardware implementations.

In accordance with various embodiments of the present disclosure, themethods described herein are intended for operation as software programsrunning on a computer processor. Furthermore, software implementationscan include, but not limited to, distributed processing orcomponent/object distributed processing, parallel processing, or virtualmachine processing can also be constructed to implement the methodsdescribed herein.

The present disclosure contemplates a machine readable medium containinginstructions 274, or that which receives and executes instructions 274from a propagated signal so that a device connected to a networkenvironment 276 can send or receive voice, video or data, and tocommunicate over the network 276 using the instructions 274. Theinstructions 274 may further be transmitted or received over a network276 via the network interface device 270.

While the machine-readable medium 272 is shown in an example embodimentto be a single medium, the term “machine-readable medium” should betaken to include a single medium or multiple media (e.g., a centralizedor distributed database, and/or associated caches and servers) thatstore the one or more sets of instructions. The term “machine-readablemedium” shall also be taken to include any medium that is capable ofstoring, encoding or carrying a set of instructions for execution by themachine and that cause the machine to perform any one or more of themethodologies of the present disclosure.

The term “machine-readable medium” shall accordingly be taken toinclude, but not be limited to: solid-state memories such as a memorycard or other package that houses one or more read-only (non-volatile)memories, random access memories, or other re-writable (volatile)memories; magneto-optical or optical medium such as a disk or tape; andcarrier wave signals such as a signal embodying computer instructions ina transmission medium; and/or a digital file attachment to e-mail orother self-contained information archive or set of archives isconsidered a distribution medium equivalent to a tangible storagemedium. Accordingly, the disclosure is considered to include any one ormore of a machine-readable medium or a distribution medium, as listedherein and including art-recognized equivalents and successor media, inwhich the software implementations herein are stored.

Although the present specification describes components and functionsimplemented in the embodiments with reference to particular standardsand protocols, the disclosure is not limited to such standards andprotocols. Each of the standards for Internet and other packet switchednetwork transmission (e.g., TCP/IP, UDP/IP, HTML, HTTP) representexamples of the state of the art. Such standards are periodicallysuperseded by faster or more efficient equivalents having essentiallythe same functions. Accordingly, replacement standards and protocolshaving the same functions are considered equivalents.

FIG. 13 is an illustration of a communication network 280 formeasurement and reporting in accordance with an exemplary embodiment.Briefly, the communication network 280 expands broad data connectivityto other devices or services. As illustrated, the measurement andreporting system 304 can be communicatively coupled to thecommunications network 280 and any associated systems or services.

As one example, measurement system 304 can share its parameters ofinterest (e.g., angles, load, balance, distance, alignment,displacement, movement, rotation, and acceleration) with remote servicesor providers, for instance, to analyze or report on surgical status oroutcome. This data can be shared for example with a service provider tomonitor progress or with plan administrators for surgical monitoringpurposes or efficacy studies. The communication network 280 can furtherbe tied to an Electronic Medical Records (EMR) system to implementhealth information technology practices. In other embodiments, thecommunication network 280 can be communicatively coupled to HIS HospitalInformation System, HIT Hospital Information Technology and HIM HospitalInformation Management, EHR Electronic Health Record, CPOE ComputerizedPhysician Order Entry, and CDSS Computerized Decision Support Systems.This provides the ability of different information technology systemsand software applications to communicate, to exchange data accurately,effectively, and consistently, and to use the exchanged data.

The communications network 280 can provide wired or wirelessconnectivity over a Local Area Network (LAN) 292, a Wireless Local AreaNetwork (WLAN) 288, a Cellular Network 294, and/or other radio frequency(RF) system (see FIG. 4 ). The LAN 292 and WLAN 288 can becommunicatively coupled to the Internet 296, for example, through acentral office. The central office can house common network switchingequipment for distributing telecommunication services. Telecommunicationservices can include traditional POTS (Plain Old Telephone Service) andbroadband services such as cable, HDTV, DSL, VoIP (Voice over InternetProtocol), IPTV (Internet Protocol Television), Internet services, andso on.

The communication network 280 can utilize common computing andcommunications technologies to support circuit-switched and/orpacket-switched communications. Each of the standards for Internet 296and other packet switched network transmission (e.g., TCP/IP, UDP/IP,HTML, HTTP, RTP, MMS, SMS) represent examples of the state of the art.Such standards are periodically superseded by faster or more efficientequivalents having essentially the same functions. Accordingly,replacement standards and protocols having the same functions areconsidered equivalent.

The cellular network 294 can support voice and data services over anumber of access technologies such as GSM-GPRS, EDGE, CDMA, UMTS, WiMAX,2G, 3G, WAP, software defined radio (SDR), and other known technologies.The cellular network 294 can be coupled to base receiver 290 under afrequency-reuse plan for communicating with mobile devices 282.

The base receiver 290, in turn, can connect the mobile device 282 to theInternet 296 over a packet switched link. The internet 296 can supportapplication services and service layers for distributing data from themeasurement system 304 to the mobile device 282. Mobile device 282 canalso connect to other communication devices through the Internet 296using a wireless communication channel.

The mobile device 282 can also connect to the Internet 296 over the WLAN288. Wireless Local Access Networks (WLANs) provide wireless accesswithin a local geographical area. WLANs are typically composed of acluster of Access Points (APs) 284 also known as base stations. Themeasurement system 304 can communicate with other WLAN stations such aslaptop 286 within the base station area. In typical WLANimplementations, the physical layer uses a variety of technologies suchas 802.11b or 802.11g WLAN technologies. The physical layer may useinfrared, frequency hopping spread spectrum in the 2.4 GHz Band, directsequence spread spectrum in the 2.4 GHz Band, or other accesstechnologies, for example, in the 5.8 GHz ISM band or higher ISM bands(e.g., 24 GHz, etcetera).

By way of the communication network 280, the measurement system 304 canestablish connections with a remote server 298 on the network and withother mobile devices for exchanging data. The remote server 298 can haveaccess to a database 300 that is stored locally or remotely and whichcan contain application specific data. The remote server 298 can alsohost application services directly, or over the Internet 296.

It should be noted that very little data exists on implanted orthopedicdevices. Most of the data is empirically obtained by analyzingorthopedic devices that have been used in a human subject or simulateduse. Wear patterns, material issues, and failure mechanisms are studied.Although, information can be garnered through this type of study it doesyield substantive data about the initial installation, post-operativeuse, and long term use from a measurement perspective. Just as eachperson is different, each device installation is different havingvariations in initial loading, balance, and alignment. Having measureddata and using the data to install an orthopedic device will greatlyincrease the consistency of the implant procedure thereby reducingrework and maximizing the life of the device. In at least one exemplaryembodiment, the measured data can be collected to a database where itcan be stored and analyzed. For example, once a relevant sample of themeasured data is collected, it can be used to define optimal initialmeasured settings, geometries, and alignments for maximizing the lifeand usability of an implanted orthopedic device.

While the present invention has been described with reference toparticular embodiments, those skilled in the art will recognize thatmany changes may be made thereto without departing from the spirit andscope of the present invention. Each of these embodiments and obviousvariations thereof is contemplated as falling within the spirit andscope of the invention.

What is claimed is:
 1. A method of measuring leg alignment, comprisingthe steps of: coupling a tri-axial gyroscope to a tibia of a leg;providing measurement data from the tri-axial gyroscope to a computer asthe leg undergoes at least one movement; measuring a length of the tibiaof the leg; providing the tibia measurements to the computer wherein thecomputer stores the length of the tibia in memory and wherein the lengthof the tibia of the leg is used to calculate a knee frontal angle; anddisplaying an alignment measurement of the leg on a display coupled tothe computer.
 2. The method of claim 1, further including the steps of:identifying at least two bone landmarks of the tibia; measuring adistance between the at least two bone landmarks of the tibia; andcalculating the length of the tibia from the distance between the atleast two bone landmarks of the tibia.
 3. The method of claim 1, whereinthe step of measuring the length of the tibia of the leg furtherincludes a step of measuring from a bottom of a foot to a lateralcondyle of a femur of the leg.
 4. The method of claim 1, wherein a firstmovement of the leg comprises the steps of: placing the leg inextension; rotating the leg about a hip and an ankle; and sending themeasurement data from the tri-axial gyroscope.
 5. The method of claim 4,further including a step of rotating the leg about the hip and the ankleat greater than 1.5 radians/second but less than 8.0 radians/second. 6.The method of claim 1, wherein the length of the tibia of the leg can bedetermined from one or more images of the leg.
 7. The method of claim 1,wherein images of the tibia of the leg are provided to the computer, andwherein the computer is configured to calculate the length of the tibiaof the leg from one or more images of the leg.
 8. The method of claim 1,further including the steps of: identifying at least two bone landmarksof a femur of the leg; measuring a distance of between the at least twobone landmarks of the femur of the leg from one or more images of thefemur; and calculating the length of the femur of the leg from thedistance between the at least two bone landmarks of the femur of theleg, wherein the computer is configured to calculate the length of thefemur of the leg from one or more images of the leg.
 9. A method ofmeasuring leg alignment, comprising the steps of: measuring a length ofa tibia of a leg; installing a tibial prosthetic component to a proximalend of the tibia of the leg; placing an insert in a tibial tray of thetibial prosthetic component wherein the insert includes a tri-axialgyroscope, wherein one measurement plane of the tri-axial gyroscopecorresponds to a plane of the tibial tray or a plane of a bone cut onthe proximal end of the tibia of the leg, and wherein the leg undergoesat least one movement; transmitting measurement data related to the atleast one movement measured by the tri-axial gyroscope to a computer,wherein the tibia length of the leg is provided to the computer, whereinthe computer stores the length of the tibia of the leg in memory, andwherein the length of the tibia of the leg and the length of a femur ofthe leg is used to calculate a knee frontal angle; and calculating theknee frontal angle wherein the computer calculates the knee frontalangle from the measurement data.
 10. The method of claim 9, whereinmeasuring the length of the tibia of the leg includes a step ofmeasuring from a bottom of a foot of the leg to a lateral condyle of thefemur of the leg.
 11. The method of claim 10, wherein the at least onemovement comprises the steps of: placing the leg in extension; rotatingthe leg about a hip and an ankle; and sending measurement data from thetri-axial gyroscope to the computer during rotation of the leg.
 12. Themethod of claim 11, further including a step of rotating the leg aboutthe hip and the ankle at greater than 1.5 radians/second but less than8.0 radians/second.
 13. The method of claim 9, further including thesteps of: identifying at least two bone landmarks of the tibia of theleg; measuring a distance between the at least two bone landmarks of thetibia of the leg; and calculating the length of the tibia of the legfrom the distance between the at least two bone landmarks of the tibiaof the leg.
 14. The method of claim 9, wherein the length of the tibiaof the leg can be determined from one or more images of the leg.
 15. Themethod of claim 14, wherein images of the tibia of the leg are providedto the computer, and wherein the computer is configured to calculate thelength of the tibia of the leg from the images of the tibia of the leg.16. The method of claim 9, further including the steps of: identifyingat least two bone landmarks of the femur of the leg in one or moreimages of the leg; and calculating the length of the femur of the legfrom a distance between the at least two bone landmarks of the femur ofthe leg using one or more images of the leg.
 17. A method of measuringleg alignment, comprising the steps of: coupling a tri-axial gyroscopeto a tibia of a leg; rotating the leg about a hip and an ankle of theleg at greater than 1.5 radians/second but less than 8.0 radians/second;transmitting measurement data from the tri-axial gyroscope to a computeras the leg undergoes at least one movement; providing one or more imagesof the leg to the computer wherein the computer calculates a length ofthe tibia from the one or more images of the leg, wherein the computerstores the length of the tibia in memory, and wherein the measurementdata and the length of the tibia of the leg is used to calculate a kneefrontal angle; and displaying an alignment measurement of the leg on adisplay coupled to the computer.
 18. The method of claim 17, furtherincluding the step of identifying at least two bone landmarks of thetibia from the one or more images of the leg, wherein the length of thetibia corresponds to a distance between the at least two bone landmarks.19. The method of claim 17, wherein the length of the tibia is measuredfrom a bottom of a foot to a lateral condyle of a femur of the leg. 20.The method of claim 17, wherein the leg is in extension when rotatingthe leg about the hip and the ankle.